5-speed Getrag

Hi,

I just replaced the gearbox in my son's 1986 280GE. It is a 5-speed manual Getrag box, and was replaced due to syncring failure.

The 'new' box, however, has a rather whiney noise on 2nd and 3rd gear, almost like it was reversing.

I thought I'd change the oil, but wanted to ask first if anyone knew what this indicates...

Anyone..?

Kind regards,
Bard Thomas